The German billionaires behind the $10bn bid for Avon Products cosmetics group plan to sell £1.3bn of shares in Reckitt Benckiser, the FTSE 100 consumer goods group.

JAB, the Vienna-based investment company owned by the four adopted children of Albert Reimann, is the largest shareholder in Reckitt, which owns brands such as Dettol, Strepsils and Nurofen, with a 15.5% stake. After the market closed on Wednesday, JAB said it intended to sell 36m Reckitt shares, equivalent to 4.9% of the company. Reckitt shares closed 11p higher at £35.66.

The placing will raise funds for the Avon deal. JAB owns 80% of Coty, which makes Calvin Klein fragrances and is run by former Reckitt boss Bart Becht. He is trying to persuade Avon shareholders to back a deal that would see the US cosmetics company pass into private ownership.

Liberum Capital analyst Pablo Zuanic said: "We see this as a way for JAB to help Coty fund the (unsolicited) bid for Avon or for other companies that Coty may decide to pursue ... Coty has made the right move in approaching Avon. There is no conflict on pricing (as long as direct selling does not undercut the trade) and in emerging markets direct sales can help advertise the brands over time."

Avon, founded in 1886, has grown into the world's largest direct seller of cosmetics and sells a lipstick every four seconds. Coty was founded more than a century ago as a small perfume manufacturer on the outskirts of Paris and became the world's largest seller of mass-market fragrances in 2005 when it bought Unilever's perfume business.

"The sale of the placing shares reflects JAB's desire to diversify its portfolio and invest in new opportunities," said JAB. "Reckitt Benckiser remains JAB's most important investment."

The reclusive Reimanns inherited JAB (Joh A Benckiser) from their father and their combined wealth is estimated at about $20bn. Johann Adam Benckiser founded his eponymous chemical company in Pforzheim, Germany, in 1823 and was joined five years later by chemist Ludwig Reimann. JAB floated Benckiser, maker of Vanish and Cillit Bank, on the Amsterdam stock exchange in 1997. Two years later, the company merged with British firm Reckitt & Colman to create Reckitt Benckiser.

JAB stressed that it would retain its representative on Reckitt's board and a minimum shareholding of at least 10%. It said it was a "strong believer" in the company's new management team and its recently announced strategy. The investment firm committed not to sell any more Reckitt shares in the next 12 months after the completion of the placing.

Bank of America Merrill Lynch will sell the shares to institutional shareholders. The price has not been determined.

Reckitt's new chief executive, Rakesh Kapoor, wants to focus on emerging markets, along with health and hygiene. His target is to generate half of the group's sales from emerging markets by 2016. Burgeoning middle classes in India, Brazil and China are driving demand for more hygiene and health products.